Unlike other humidifiers that grow slimy mold and mildew, the Pureguardian 10-Hour* Ultrasonic Humidifier uses Silver Clean technology to fight the growth of mold and mildew on the surface of the water tank. Thanks to ultrasonic technology it is ultra-quiet when it runs making it ideal to have on while you sleep. The humidifier emits a soothing cool mist, and a low water indicator light lets you know when it's time to refill the water tank. Night light feature makes it a great addition to kid's